Invasive breast cancer, the most common nonskin cancer in American women, was diagnosed in approximately 184,000 women in the United States in 2000, and let to approximately 41,000 deaths (Nancy E. Davidson. 2001. “Breast Cancer”, Section 12 Part VII In Scientific American Medicine. Edward Rubenstein and Daniel D. Federman eds., Scientific American, Inc.: New York, N.Y.). Current guidelines for breast cancer screening recommended by the American Cancer Society and the National Cancer Institute include monthly breast self examination for all women older than 20 years and annual mammography for women older than 40 years who are at standard risk for breast cancer. For those at higher risk, current practice advocates that mammographic screening begin at 25 years of age or five years earlier than the age of the person with the earliest diagnosis of breast cancer in the immediate or extended family.
Breast cancer may present as architectural changes or microcalcifications on a mammogram, or by clinical symptoms, such as a palpable mass, nipple discharge, or skin or nipple changes. Regardless of whether the patient is symptomatic or asymptomatic, a histologic examination of the suspect tissue is mandatory to establish a diagnosis. Open incisional or excisional biopsies were commonly performed in the past to obtain tissue samples. The modern trend relies on fine-needle aspiration, core-needle biopsy, or other image guided or non-image guided percutaneous procedures, e.g., vacuum assisted biopsy using the MAMMOTOME® breast biopsy system (Ethicon Endo-Surgery, Inc., Cincinnati, Ohio), to obtain a sample of cells or tissue for diagnosis.
After any given biopsy procedure, a subsequent examination of the biopsy site is often desirable. For example, if the initial biopsy only partially removed the suspect tissue, and a malignant lesion is subsequently diagnosed, re-excision of the original biopsy site is indicated. Identification of a biopsy site is also helpful during patient follow-up examinations for reoccurrence. Thus, there is a need to determine the location, most importantly the center, as well as the orientation and margins of the subcutaneous tissue cavity from which the suspect lesion is removed.
Prior methods of marking biopsy cavities utilize one or more tissue marking clips as the biopsy site marking device. One representative marking apparatus is the MICROMARK™ II tissue marker (Biopsis Medical, Inc., Irvine, Calif.). Among other concerns, deployment of the MICROMARK™ II tissue maker is unreliable, the marker device often failing to properly attach to the cavity wall. Furthermore, because clip attachment occurs to the side, not the center of the cavity, spatial orientation and position of the cavity is difficult if not impossible during follow-up examination. Moreover, during the stereotactic breast biopsy procedure, the breast is under compression when the marking clip is placed. Upon release of the compressive force, the clip will migrate relative to the biopsy void, and the orientation as well as the location of the margins of the cavity are usually lost.
Other biopsy markers that attempt to minimize migration, e.g., after tissue is decompressed, are described in U.S. Pat. No. 6,161,034 and U.S. Pat. No. 6,347,241, both to Burbank et al.; U.S. Pat. No. 6,270,464 to Fulton, III et al.; and U.S. Pat. No. 6,350,244 and WO 01/62135, both to Fisher.
Burbank et al. describes chemical preparations of collagen or gelatin having a visible marker such as carbon particles or a dye that are introduced into biopsy cavities. The markers are imageable by mammography, fluoroscopy, CT, or MRI.
Fulton, III et al. depicts a swellable marker that may be palpably harder after delivery into the biopsy cavity. The marker is imageable by mammography, ultrasound, or MRI.
In U.S. Pat. No. 6,350,244 and WO 01/62135, Fisher describes markers that are hollow spheres made from polylactic acid. The spheres are filled with iodine or other radiopaque material to make them imageable by available radiographic techniques such as x-ray and/or ultrasound. Multiple markers are introduced to fill the biopsy cavity.
In U.S. Pat. No. 6,347,241, Burbank et al. describes a marker body that includes a pre-shaped pellet formed of bioabsorbable material having a plurality of gas bubbles dispersed therein which are configured to facilitate ultrasonic observation of the pellet at a biopsy site within a patient and having an X-ray detectable element of specific predetermined non-biological configuration embedded therein.
Although the above mentioned marker devices address some of the problems associated with clip-type markers, the problem of prolonged monitoring of a biopsy site still remains. Thus, it would be of considerable medical benefit to be able to permanently mark the location of a biopsy cavity, especially after a percutaneous biopsy procedure.